Serum 25-hydroxyvitamin D and elderly skeletal muscle mass and function in urban north China

Background and Objectives: To investigate the association of serum 25-hydroxyvitamin D (25(OH)D) with skeletal muscle mass (SMM) and function among the elderly in an urban area in northern China. Methods and Study Design: A total of 912 participants (316 men, 596 women) aged more than 60 years from 4 communities in Beijing were enrolled. Serum concentrations of 25(OH)D were measured through radioimmunoassay. SMM was assessed through bioelectrical impendence analysis, whereas skeletal muscle function was assessed through grip strength and 4-m regular gait speed measurements. On the basis of expert consensus of the Asian Working Group for Sarcopenia, low muscle mass was defined as relative skeletal mass index (RSMI) <7.0 kg/m(2) for men and <5.7 kg/m(2) for women. A noncondition logistical regression model was employed to explore the association between vitamin D and both muscle mass and function. Results: Serum 25(OH)D was positively associated with grip strength (beta=0.16, SE=0.05). The upper quartile of 25(OH)D was negatively associated with loss of grip strength (OR=0.05, 95% CI: 0.01-0.48) in men but not in women. No significant associations were noted between 25(OH)D and appendicular skeletal muscle mass, RSMI, and gait speed. Conclusions: The present study demonstrated a positive association between vitamin D and skeletal muscle strength in elderly Chinese men but not women.